Semiconductor devices are manufactured or fabricated on semiconductor wafers using a number of different processing steps to create transistor and interconnection elements. To electrically connect transistor terminals associated with the semiconductor wafer, conductive (e.g., metal) trenches, vias, and the like are formed in dielectric materials as part of the semiconductor device. The trenches and vias couple electrical signals and power between transistors, internal circuit of the semiconductor devices, and circuits external to the semiconductor device.
In forming the interconnection elements the semiconductor wafer may undergo, for example, masking, etching, and deposition processes to form the semiconductor transistors and desired electronic circuitry to connect those transistor terminals. In particular, multiple masking, ion implantation, annealing, and plasma etching, and chemical and physical vapor deposition steps can be performed to form shallow trench, transistor well, gate, poly-silicon line, and interconnection line structures. In each step, particle and contamination are added on front and backside of the wafer. Those particle and contamination can lead to defects on wafers and subsequently lowering the IC device yield. In order to remove the particle and contamination, wet bench equipments have been used for many years. A wet bench equipment simultaneously processes a batch of wafers (normally 25 wafers) in a polarity of wet baths in a sequential fashion. In between two baths, the processed batch of wafers is rinsed to remove any residue cleaning solution from the previous bath. In a wet bench equipment, flow velocity of the cleaning solution between the separation among wafers is relatively low, thereby the cleaning efficiency, especially for smaller particles, is limited. The queue time for the batch of wafer to transfer from one bath to another is difficult to control as the time requirement for each clean step is different, thereby a high process variation is unavoidable. Furthermore, cross contamination from one wafer to another in the same batch is inherent for a batch process. As wafer size migrates to 300 mm, and manufacture technology node advances to 65 nm and beyond, traditional wet bench approach can no longer effectively and reliably cleaning the particles and contamination from wafer.
Single wafer cleaning equipment has become an alternative choice. Single wafer cleaning equipment processes one wafer a time in a cleaning module, sequentially injecting multiple cleaning solutions onto its surface and applying a deionized (DI) water rinse between cleaning solutions. Single wafer processor gives the benefits to precisely control wafer rotation, cleaning solution dispense time, and eliminate wafer to wafer cross contamination. In order to save cleaning solution, and to reduce cost for waste chemical treatment, It is desired to recycle or reuse those cleaning solutions. However, since all cleaned steps are performed in one cleaning chamber, it is a challenge to recycle or reclaim those cleaning solutions without cross contamination at part per million (ppm) level. The less the cross contamination, the less impact it does to the cleaning process and the longer the lifetime of the cleaning solution is.
It is desired to have a robust and precisely controlled cleaning solution recycle or reclaim method for reducing chemical cross contamination, and therefore to extend the life time of recycled or reclaimed cleaning solution.